Preparation method of glass-coated silicon nitride ceramic powder and silicon nitride ceramic
By coating the surface of silicon nitride powder with a glass layer, the problem of high light absorption of silicon nitride powder was solved, the photocuring depth and printing efficiency were improved, and the preparation of high-performance silicon nitride ceramics was realized.
Patent Information
- Application Number
- CN202511110995.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-08
- Publication Date
- 2025-11-11
AI Technical Summary
The high absorbance of silicon nitride powder results in poor ultraviolet light penetration, which limits the depth and efficiency of photopolymerization printing.
By mixing glass powder with silicon nitride powder and calcining it under vacuum, the glass powder melts and coats the surface of the silicon nitride powder, forming a uniform glass coating layer. This reduces the light absorption and refractive index of the powder and improves its photocuring performance.
This significantly improves the photopolymerization depth and printing efficiency of silicon nitride ceramics, providing a foundation for the preparation of high-performance silicon nitride ceramics with complex structures.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of silicon nitride photocuring technology, and more particularly to a method for preparing glass-coated silicon nitride ceramic powder and silicon nitride ceramic. Background Technology
[0002] Silicon nitride is a widely used ceramic with excellent flexural strength and fracture toughness, making it a highly regarded key material in extreme environments. Its excellent thermal conductivity also makes it widely used in the semiconductor field.
[0003] Photopolymerization printing technology has enabled the rapid prototyping of silicon nitride ceramics with high precision and complex geometries, overcoming the limitations of traditional processing methods. However, the extremely high absorbance of silicon nitride powder severely hinders the penetration of ultraviolet light, resulting in very low curing depth of the slurry. This characteristic not only significantly reduces printing efficiency but also significantly increases the difficulty of the printing process. Therefore, how to effectively improve the curing depth of silicon nitride ceramic powder in the photopolymerization printing process has become a core technical challenge that urgently needs to be solved in this field. Summary of the Invention
[0004] The technical problem to be solved by this invention is how to improve the photocuring depth of silicon nitride and improve the photocuring performance of silicon nitride ceramics.
[0005] To address the above problems, the present invention proposes the following technical solution:
[0006] In a first aspect, the present invention provides a method for preparing glass-coated silicon nitride ceramic powder, comprising:
[0007] Glass powder and silicon nitride powder are mixed evenly by ball milling at a mass ratio of 1:5 to 10, and then calcined under vacuum for 1 to 3 hours. After cooling in the furnace, the product is crushed and sieved to obtain glass-coated silicon nitride ceramic powder. The calcination temperature is the temperature at which the glass powder is completely melted.
[0008] Furthermore, the ball milling parameters are 300–400 rpm, 4–8 h.
[0009] Furthermore, the glass powder has a particle size of 0.1–10 μm, and the silicon nitride powder has a particle size of 0.1–10 μm.
[0010] Furthermore, the glass powder is silicate glass powder.
[0011] Furthermore, the melting point of the glass powder is below 1200°C, and the calcination temperature is above the melting point of the glass powder and can completely melt the glass powder.
[0012] Furthermore, the melting point of the glass powder is 500–1100°C, and the calcination temperature is 600–1200°C.
[0013] Furthermore, the sieving is performed through a 100-300 mesh sieve.
[0014] Secondly, the present invention provides a method for preparing silicon nitride ceramics, comprising the following steps:
[0015] Glass-coated silicon nitride ceramic powder and sintering aid were ball-milled and mixed to obtain a mixed powder.
[0016] The mixed powder is formulated with a photocurable resin and a photoinitiator to prepare a photocurable ceramic slurry.
[0017] The photocurable ceramic slurry is photocured and then degreased and sintered to obtain silicon nitride ceramic.
[0018] The glass-coated silicon nitride ceramic powder is prepared by the method described in the first aspect.
[0019] Furthermore, the particle size of the sintering aid is 0.1–10 μm.
[0020] Furthermore, the sintering aid includes at least one of metal oxides, rare earth element oxides, and non-oxide sintering aids, such as magnesium oxide and yttrium oxide.
[0021] Furthermore, the solid content of the photocurable ceramic slurry is 50-60 vol%.
[0022] Furthermore, the degreasing is a two-step method of vacuum degreasing and air degreasing. First, the organic matter in the green body is heated to 500°C in a vacuum environment to turn into carbon, and then heated to 450°C in air to remove the carbon in the green body, so as to obtain a green body composed only of silicon nitride, silicon dioxide and sintering aids.
[0023] Furthermore, the sintering process includes atmospheric pressure sintering, gas pressure sintering, and spark plasma sintering.
[0024] The present invention also provides a silicon nitride ceramic, which is prepared by the method for preparing silicon nitride ceramic described in the second aspect.
[0025] Compared with the prior art, the technical effects achieved by the present invention include:
[0026] The present invention provides a method for preparing glass-coated silicon nitride ceramic powder. By precisely controlling the mass ratio of glass powder to silicon nitride powder and employing ball milling for thorough mixing, the uniformity of the initial contact between the two materials is ensured. Subsequently, calcination is performed in a vacuum environment at a specific temperature, sufficient to completely melt the glass powder into a liquid phase. The molten glass, under vacuum conditions, fully wets and uniformly coats the surface of the silicon nitride particles, effectively isolating the silicon nitride from air and altering the optical properties of the silicon nitride powder surface. After calcination and furnace cooling, the molten glass solidifies to form a stable and complete coating layer. Further crushing and sieving processes yield a silicon nitride ceramic composite powder with a uniformly covered glass layer and controllable particle size. This method significantly improves the overall light transmittance of the powder, overcoming the adverse effects of excessively high light absorption of silicon nitride powder on the photopolymerization process. This greatly improves its adaptability in photopolymerization 3D printing processes, laying a powder material foundation for the efficient fabrication of high-performance, complex-structure silicon nitride ceramic components.
[0027] Furthermore, since the main component of glass is silicon dioxide, which is colorless and transparent, directly using silicon dioxide raw materials for coating has the problem of excessively high melting point (1700℃). However, some low-melting-point glasses have melting points below 1200℃, have low operation requirements, and the coating temperature does not affect the performance of silicon nitride itself, and can effectively improve the photocuring performance of silicon nitride ceramics.
[0028] The method for preparing silicon nitride ceramics provided by this invention uses glass-coated silicon nitride ceramic powder as raw material. Coating the surface of silicon nitride powder can greatly reduce the light absorption and refractive index of the powder, thereby solving the problem that silicon nitride powder particles have high light absorption and refractive index and are difficult to be penetrated by ultraviolet light, providing a new idea for the photocuring preparation of silicon nitride ceramics. Detailed Implementation
[0029] The technical solutions in the embodiments will be clearly and completely described below. Obviously, the embodiments described below are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.
[0030] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.
[0031] It should also be understood that the terminology used in this specification of embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to limit the embodiments of the invention. As used in this specification of embodiments of the invention and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.
[0032] It should be noted that, in order to facilitate the explanation of the beneficial effects of the present invention in photopolymerization printing, the following embodiments, when testing the curing performance of silicon nitride slurry, use ceramic slurry with the same solid content, set the same printer light intensity, and use the same curing time. The thickness of the printed silicon nitride monolayer is measured by a spiral micrometer, and the curing performance is evaluated by the thickness value.
[0033] Example 1
[0034] This invention provides a method for preparing a photocurable ceramic slurry from glass-coated silicon nitride ceramic powder, and for photocuring silicon nitride. It also provides a method for preparing the glass-coated silicon nitride ceramic powder. Details are as follows:
[0035] Step 1: Weigh silicon nitride powder and bismuth silicate glass (containing 70% silicon) in a mass ratio of 95:5 according to the mass ratio, pour them into a polytetrafluoroethylene ball mill jar, add an appropriate amount of silicon nitride grinding balls and anhydrous ethanol, and ball mill at 350 rpm for 4 hours to obtain a uniformly mixed suspension; then dry it by rotary evaporation, and pass the dried powder through a 100-mesh sieve to obtain a first powder with uniform particles and high dispersibility.
[0036] Step 2: Take the first powder obtained in Step 1 and place it in an alumina crucible. Heat it in a tube furnace and keep it at 850℃ for 2 hours. Then cool it slowly. Take out the calcined material, crush it with a crusher, and grind it through a 100-mesh sieve to obtain glass-coated silicon nitride ceramic powder.
[0037] Step 3:
[0038] (1) Take the glass-coated silicon nitride ceramic powder, magnesium oxide and yttrium oxide prepared in step 2, weigh them in a mass ratio of 93:5:2, add them to a polytetrafluoroethylene ball mill jar, and ball mill them at a speed of 350 rpm for 4 hours; dry the resulting suspension by rotary evaporation, pass it through a 100-mesh sieve, and obtain a mixed powder that can be used for photopolymerization printing, labeled as a1 powder;
[0039] (2) Take silicon nitride powder, magnesium oxide and yttrium oxide that have not been treated in steps one and two, weigh them in a mass ratio of 93:5:2, add them to a polytetrafluoroethylene ball mill jar, and ball mill them at a speed of 350 rpm for 4 hours; dry the resulting suspension by rotary evaporation, pass it through a 100-mesh sieve, and obtain a mixed powder that can be used for photopolymerization printing, labeled as a2 powder.
[0040] Step Four:
[0041] (1) The two powders a1 and a2 prepared in step 3 were mixed with the same mass of photocurable resin trimethylolpropane triacrylate and photoinitiator 2,4,6-trimethylbenzoyl-diphenylphosphine oxide to prepare two slurries with a solid content of 50 vol%. The slurry containing glass-coated silicon nitride ceramic powder was labeled A1, and the slurry containing untreated silicon nitride powder was labeled A2.
[0042] (2) Adjust the printing parameters to maintain the light source intensity at 60mW / cm². 2 Single-layer printing tests were conducted on both types of inks, with a uniform exposure time of 5 seconds. The thickness of the single layer printed by the two inks was measured. A1 was 38 μm, and A2 was 28 μm.
[0043] Example 2
[0044] Step 1: Weigh silicon nitride powder and borosilicate glass (silicon content 75%) in a mass ratio of 90:10, pour them into a polytetrafluoroethylene ball mill jar, add an appropriate amount of silicon nitride grinding balls and anhydrous ethanol, and ball mill at 350 rpm for 4 hours to obtain a uniformly mixed suspension; then dry it by rotary evaporation, and pass the dried powder through a 100-mesh sieve to obtain a first powder with uniform particles and high dispersibility.
[0045] Step 2: Take the first powder obtained in Step 1 and place it in an alumina crucible. Heat it in a tube furnace and keep it at 1200℃ for 2 hours. Then cool it slowly. Take out the calcined material, crush it with a crusher, and grind it through a 100-mesh sieve to obtain glass-coated silicon nitride ceramic powder.
[0046] Step 3:
[0047] (1) Take the glass-coated silicon nitride ceramic powder, gadolinium oxide and yttrium oxide prepared in step 2, weigh them in a mass ratio of 92:6:2, add them to a polytetrafluoroethylene ball mill jar, and ball mill them at a speed of 350 rpm for 4 hours; dry the resulting suspension by rotary evaporation, pass it through a 100-mesh sieve, and obtain a mixed powder that can be used for photopolymerization printing, labeled as b1 powder;
[0048] (2) Take silicon nitride powder, gadolinium oxide and yttrium oxide that have not been treated in steps one and two, weigh them in a mass ratio of 92:6:2, add them to a polytetrafluoroethylene ball mill jar, and ball mill them at a speed of 350 rpm for 4 hours; dry the resulting suspension by rotary evaporation, pass it through a 100-mesh sieve, and obtain a mixed powder that can be used for photopolymerization printing, which is labeled as b2 powder.
[0049] Step Four:
[0050] (3) The b1 and b2 powders prepared in step 3 were mixed with the same mass of photocurable resin (trimethylolpropane triacrylate) and photoinitiator (2,4,6-trimethylbenzoyl-diphenylphosphine oxide) to prepare two slurries with a solid content of 50 vol%. The slurry containing glass-coated silicon nitride ceramic powder was labeled B1, and the slurry containing untreated silicon nitride powder was labeled B2.
[0051] Adjust the printing parameters to maintain a light source intensity of 60mW / cm². 2 Single-layer printing tests were conducted on both types of inks, with a uniform exposure time of 5 seconds. The thickness of the single layer printed by the two inks was measured. B1 was 40 μm, and B2 was 25 μm.
[0052] Example 3
[0053] Step 1: Weigh silicon nitride powder and aluminosilicate glass (silicon content 50%) in a ratio of 95:5 by weight, pour them into a polytetrafluoroethylene ball mill jar, add an appropriate amount of silicon nitride grinding balls and anhydrous ethanol, and ball mill at 350 rpm for 6 hours to obtain a uniformly mixed suspension; then dry it by rotary evaporation, and pass the dried powder through a 100-mesh sieve to obtain a first powder with uniform particles and high dispersibility.
[0054] Step 2: Take the first powder obtained in Step 1 and place it in an alumina crucible. Heat it in a tube furnace and keep it at 950℃ for 2 hours. Then cool it slowly. Take out the calcined material, crush it with a crusher, and grind it through a 100-mesh sieve to obtain glass-coated silicon nitride ceramic powder.
[0055] Step 3:
[0056] (1) Take the glass-coated silicon nitride ceramic powder, alumina and yttrium oxide prepared in step 2, weigh them in a mass ratio of 93:5:2, add them to a polytetrafluoroethylene ball mill jar, and ball mill them at a speed of 350 rpm for 6 hours; dry the resulting suspension by rotary evaporation, pass it through a 100-mesh sieve, and obtain a mixed powder that can be used for photopolymerization printing, labeled as C1 powder;
[0057] (2) Take silicon nitride powder, alumina and yttrium that have not been treated in steps one and two, weigh them in a mass ratio of 93:5:2, add them to a polytetrafluoroethylene ball mill jar, and ball mill them at a speed of 350 rpm for 6 hours; dry the resulting suspension by rotary evaporation, pass it through a 100-mesh sieve, and obtain a mixed powder that can be used for photopolymerization printing, which is labeled as C2 powder.
[0058] Step Four:
[0059] (4) The C1 and C2 powders prepared in step 3 were mixed with the same mass of photocurable resin (trimethylolpropane triacrylate) and photoinitiator (2,4,6-trimethylbenzoyl-diphenylphosphine oxide) to prepare two slurries with a solid content of 50 vol%. The slurry containing glass-coated silicon nitride ceramic powder was labeled C1, and the slurry containing untreated silicon nitride powder was labeled C2.
[0060] Adjust the printing parameters to maintain a light source intensity of 60mW / cm². 2 Single-layer printing tests were conducted on both types of inks, with a uniform exposure time of 5 seconds. The thickness of the single layer printed by the two inks was measured. C1 was 30 μm, and C2 was 26 μm.
[0061] Table 1 summarizes the test results of the slurry curing performance of each embodiment.
[0062] Table 1. Curing performance test results of silicon nitride ceramic slurries in each embodiment.
[0063]
[0064] The results above show that the slurry containing the coated powder has a higher curing depth. This is because the coated powder is a layer of transparent glass coated on the surface of silicon nitride, which can greatly reduce the light absorption and refractive index of the silicon nitride powder, making it easier for ultraviolet light to penetrate the silicon nitride ceramic slurry, thereby obtaining better curing performance. Furthermore, the results in the table also indicate that the higher the silica content of the glass, the more significant the improvement in the curing depth of the silicon nitride slurry. Using the method of the present invention to coat silicon nitride powder with borosilicate glass (silicon content 75%), the prepared silicon nitride slurry has a higher curing depth after curing.
[0065] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.
[0066] The above description describes specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.
Claims
1. A method for preparing glass-coated silicon nitride ceramic powder, characterized in that, include: Glass powder and silicon nitride powder are mixed evenly by ball milling at a mass ratio of 1:5 to 10, and then calcined under vacuum for 1 to 3 hours. After cooling in the furnace, the product is crushed and sieved to obtain glass-coated silicon nitride ceramic powder. The calcination temperature is the temperature at which the glass powder is completely melted.
2. The method for preparing glass-coated silicon nitride ceramic powder as described in claim 1, characterized in that, The glass powder has a particle size of 0.1–10 μm, and the silicon nitride powder has a particle size of 0.1–10 μm.
3. The method for preparing glass-coated silicon nitride ceramic powder as described in claim 1, characterized in that, The glass powder is silicate glass powder.
4. The method for preparing glass-coated silicon nitride ceramic powder as described in claim 1, characterized in that, The melting point of the glass powder is below 1200°C, and the calcination temperature is above the melting point of the glass powder and can completely melt the glass powder.
5. The method for preparing glass-coated silicon nitride ceramic powder as described in claim 4, characterized in that, The melting point of the glass powder is 500-1000℃, and the calcination temperature is 600-1200℃.
6. A method for preparing silicon nitride ceramics, characterized in that, Includes the following steps: Glass-coated silicon nitride ceramic powder and sintering aid were ball-milled and mixed to obtain a mixed powder. The mixed powder is formulated with a photocurable resin and a photoinitiator to prepare a photocurable ceramic slurry. The photocurable ceramic slurry is photocured and then degreased and sintered to obtain silicon nitride ceramic. The glass-coated silicon nitride ceramic powder is prepared by the method described in any one of claims 1-5.
7. The method for preparing silicon nitride ceramic as described in claim 6, characterized in that, The particle size of the sintering aid is 0.1–10 μm.
8. The method for preparing silicon nitride ceramic as described in claim 6, characterized in that, The sintering aid includes at least one of metal oxides, rare earth element oxides, and non-oxide sintering aids.
9. The method for preparing silicon nitride ceramic as described in claim 6, characterized in that, The solid content of the photocurable ceramic slurry is 50-60 vol%.
10. A silicon nitride ceramic, characterized in that, The silicon nitride ceramic is prepared by the method described in any one of claims 6-9.